1. Field of the Invention
The present invention relates to a method of and apparatus for detecting diseased tissue. In particular, the present invention provides a noninvasive method of detecting diseased tissue by sensing skin temperature, the homogeneity thereof, the temporal variation thereof and the correlation thereof using a sensor detecting two different bands of infrared wavelengths.
2. Description of Related Art
In the field of diseased or cancerous tissue detection, many methods require subjecting the patient to doses of X-ray radiation or to painful biopsies, especially for breast cancer detection. More recently, researchers discovered that dysfunction of the neuronal control of the vasculature due to cancerous lesions leads to temporal or periodic perfusion changes. By measuring, recording and analyzing these periodic perfusion changes, typically through infrared (IR) imaging, diseased or cancerous tissue can be detected. While these periodic perfusion changes appear to be associated with most types of diseased or cancerous tissue, skin cancer and other cancers near the surface of the skin are most likely to be detected using IR imaging. Such a method is described in U.S. Pat. Nos. 5,810,010, 5,961,466 and 5,999,843, all to Michael Anbar, and hereby incorporated by reference.
In particular, breast cancer appears to be very susceptible to detection through IR imaging. Breast cancer detection by this method involves taking a series of IR images of the breast. This series of IR images will show both neuronal control and non-neuronal control of periodic perfusion changes in a cancerous breast. These IR images are then converted into thermal images with a temperature associated with each portion of the thermal image. The thermal images are then analyzed by finding the average temperature and standard deviation of temperature for each subarea within the thermal images. Clusters of subareas having abnormal average temperatures or standard deviations are indicative of cancer. It is anticipated that breast cancer may generally be detected by imaging the appropriate lymph nodes, the so-called “signal nodes,” which tend to have increased biological activity if cancer is present.
The frequency of the periodic perfusion changes can also be used to detect cancer. Neuronal control generally has a lower frequency than non-neuronal control of periodic perfusion. Therefore, by analyzing the thermal images and determining the periodic perfusion frequency for each of the subareas, clusters of subareas having higher frequencies are indicative of cancer.
The use of IR images for cancer detection places very stringent requirements on an IR imager. The small temperature changes associated with neuronal and non-neuronal perfusion require an IR imager sensitivity of less than 0.01° C. While IR imagers having this level of sensitivity have been demonstrated, these IR imagers have not successfully been built in quantity.
In view of the desirability of non-invasive means of cancer detection that do not require subjecting the patient to X-ray radiation exposure, there exists a need for a method that places lower requirements upon IR imager sensitivity. A method that requires lower sensitivity will lead to increased manufacturability and lower IR imager cost. Lower cost IR imagers can lead to greater accessibility to cancer screening and detection.